L-89-246, Forwards Outline of Spent Fuel Pool Boraflex Panels Integrity Assessment Program to Be Conducted by Util to Meet Condition Imposed by ASLBP

Forwards Outline of Spent Fuel Pool Boraflex Panels Integrity Assessment Program to Be Conducted by Util to Meet Condition Imposed by ASLBP

ML17223A224
Person / Time
Site:	Saint Lucie
Issue date:	07/10/1989
From:	Woody C FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
88-560-01-LA, 88-560-1-LA, L-89-246, NUDOCS 8907180059
Download: ML17223A224 (9)

Text

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ACCESSION NBR:8907180059 DOC.DATE-89/07/10 NOTARIZED: NO FACIL:50-335 St. Lucie Plant, Unit 1, Florida Power

& Light Co.

AUTH.NAME AUTHOR AFFILIATION WOODY,C.O.

Floillda Power

& Light Co.

'r'l ~t,r RECIP.NAME RECIPIENT AFFILIATION>>',,'>..'lIi,"'NQ

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Documtent,Control Branch (Document Control Desk)

SUBJECT:

Forwards outline of spent fuel pool boraflex panels integrity assessment program,per ASLB 890509 decision.

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P.O. Box14000, Juno Beach, FL 33408-0420 JULY. 1 0 1989 L-89-246 U. S. Nuclear Regulatory Commission Attn:

Document Control Desk Washington, D.

C.

20555 Gentlemen:

Re:

St. Lucie Unit, 1 Docket No. 50-335 Spent Fuel Pool Boraflex Panels Inte rit Assessment Pro ram By letter L-87-245, dated June 12,

1987, Florida Power 6 Light Company (FPL) submitted a proposed License Amendment to permit the reracking of the Spent Fuel Pool at, St. Lucie Unit 1.

The proposed License Amendment was intended to increase the storage capacity in the Spent Fuel Pool from 728 fuel assemblies to 1706 fuel assemblies.

The increased storage capacity was necessary to provide continued adequate spent fuel storage capacity for St.

Lucie Unit l.

On March 11,

1988, the NRC approved FPL's proposal and issued Amendment 91 to Facility Operating License No. DPR-67'or St. Lucie Unit l.

As a result of a hearing request, an Atomic Safety and Licensing Board (ASLB)

(ASLBP No. 88-560-Ol-LA) was convened.

Following the hearing, held in early

1989, the ASLB issued its initial decision on May 9, 1989.

The decision ruled that the license permitting reracking St. Lucie Unit 1 shall remain in full force and effect as issued.

The ASLB, however, in its decision imposed a condition.

That condition states:

That in the event that any of the Region 1 Boraflex test coupons are subjected to gamma irradiation equal to or greater than 1

x 10

rads, licensee is directed to prepare within 30 days a study program to be approved by the NRC staff and performed by the licensee to assess the effect of the irradiation on the integrity of the Boraflex panels.

The study program should include Blackness Testing or state-of-the-art equivalent approved by the NRC Staff.

pDR A O~> SSO7g-O S5'07) SO P

ADOCK OOOO PDC an FPL Group company

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U. S. Nuclear Regulatory Commission L-89-246 Page two The attached outlines the study program to be conducted by FPL to meet the condition imposed by the ASLB.

If there should be any questions, please contact us.

Very truly yours, C. 0.

Woo Acting S ior Vice President Nuclear COW/EJW/gp Attachment cc:

Stewart D. Ebneter, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant

ATTACHMENT ST ~ LUCIE UNIT 1 SPENT FUEL POOL BORAFLEZ PANELS INTEGRITY ASSESSMENT PROGRAM A one time Blackness Test (neutron logging) will be performed on selected Region 1 storage cells.

The program, will test twenty (20) storage cells by neutron logging.

The cells to be tested will be the fifteen (15) Region 1 cells which currently have stored fuel or Boraflex coupon trees" for the normal surveillance

program, and five (5) non-irradiated storage cells, which will be used to obtain baseline data.

The testing program will be controlled through the use of Florida Power

& Light Company (FPL) approved guidelines, and will meet or exceed industry standards at the time of the testing.

This one time neutron logging will be performed coincident with the long term testing required after the Boraflex coupons have been subjected to an irradiation period of one year.

This one year surveillance is scheduled for September 1989.

Descri tion of Blackness Testin Neutron Lo in Neutron logging is a method used to measure the thermal neutron attenuation in the walls of high density spent fuel storage racks.

The technique (a derivative of well-logging used in the oil industry) uses a

sealed neutron source (Cf-252) and four (4) thermal neutron detectors (BF3) to verify the continued presence and integrity of the neutron absorbing material (Boraflex) in the storage racks.

During the neutron logging operation, the testing tool (containing the source and the four (4) detectors) is lowered into the storage pool and vertically traverses selected storage cells.

As the test tool traverses the cell, fast neutrons from the source pass through the cell walls and are moderated (thermalized) in the water adjacent to the cell.

The back scatter thermal neutrons are absorbed in areas of the rack where the absorber material is present and intact.

However, in areas where the absorber material is missing or significantly degraded, the thermal neutrons will pass through the cell wall and be registered as counts by the detectors inside the test tool.

Increases in counting rates are interpreted as indicating missing absorber material in the storage cells being measured.

Bases of Pro ram The proposed program has three (3) variables:

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Frequency of Testing

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Time of Testing

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Number of Cells Tested

The testing frequency proposed is a one time neutron logging.

A one time test is adequate since the intent of the test is to detect gaps resulting from the shrinkage of Boraflex.

Radiation is the dominant contributor to shrinkage.

Gamma radiation induces cross-linkage of the polymer in Boraflex which leads to shrinkage.

As the accumulated radiation doses

increase, cross-linkage becomes saturated, and no more shrinkage will occur.

Tests performed on Boraflex show no significant changes in goraflex shrinkage at cumulative doses between 5 x 10 and 1 x 10 rads.

Also, Electric Power Research Institute (EPRI) st$ ies conclude that cross-linking saturates at approximately 1 x 10

rads, and, therefore, shrinkage stops.

The ASLB's order requires FPL to put in place a program once the radiation exposure of the test panels exceeds 1 x 10 rads.

Based on the exposure

$o date, the panels to be tested will be irradiated to about 1 x 10 rads by September 1989.

Therefore, the panels to be tested will have achieved their maximum shrinkage.

Any additional testing performed subsequent to this testing would not provide additional information.

The time that FPL has chosen to perform the test is acceptable based on several factors.

The first factor is, as stated

above, that the Boraflex panels will have achieved their maximum projected shrinkage.

Secondly, by performing the tests at the scheduled one year coupon surveillance, the specific accumulated

dose, dimensional

changes, molecular

changes, neutron attenuation, and physical characteristics will be documented as required by the long term surveillance testing.

This information can be used in conjunction with the Blackness Testing results to verify the performance of the Boraflex panels.

Additionally, by performing this neutron logging concurrent with the scheduled coupon surveillance, ALARA will be practiced by eliminating two separate surveillances in the Spent Fuel

Pool, and thus reducing exposure to plant and contract personnel.

Finally, the number of cells to be tested is adequate since the Spent Fuel Pool for St.

Lucie Unit 1 currently has only 13 fuel cells in Region 1 which have been used for spent fuel storage.

These cells are part of the long term surveillance program, and are used to store spent fuel assemblies around two cells containing the surveillance coupons (see attached Figure 1).

Therefore, performing the neutron logging on the fifteen (15) fuel and coupon storage cells (60 panels) willtest 1004 of the irradiated Boraflex panels.

In addition, five (5) storage cells that do not contain a spent fuel assembly or coupon tree will be tested (20 panels).

The results of these non-irradiated panels will be used as a

baseline data.

Calibration Prior to performing neutron logging of the subject cells, the test tool calibration and sensitivity will be demonstrated using a test cell in the St. Lucie Unit 1 Spent Fuel Pool.

The test tool will be traversed through the test cell located in the Spent Fuel Pool.

The test will contain Boraflex panels with various known defects in the Boraflex material.

The test equipment will be calibrated as necessary using the test cell prior to performing actual neutron logging.

This calibration will be performed in accordance with approved plant instructions and will demonstrate that the test is capable of detecting gaps in the Boraflex panels which are larger than 0.5 inch.

Evaluation Criteria As noted in FPL's testimony during the rerack hearing, and restated in the May 9, 1989 ASLB decision, the St. Lucie Unit 1 spent fuel racks are designed to maintain Keff < 0.95 assuming the combination of assumptions outlined below.

a.

Four percent shrinkage distributed in 0.5 inch gaps at 12 inch intervals b.

Gaps are at the same elevation in all panels

c. Unborated water, in the Spent Fuel Pool Since gaps up to 0.5 inches have been evaluated and found acceptable, any gaps identified during neutron logging which are 0.5 inches will be evaluated by FPL.

Zf necessary, additional testing and/or evaluation will be 'done.

Conclusions The information provided above demonstrates the acceptability of FPL's proposed Blackness Testing (neutron logging) Program, to meet the requirements of the ASLB order of May 9, 1989.

FPL intends to conduct neutron logging as outlined in this evaluation concurrent with the one year surveillance program scheduled for September, 1989.

Florida Po~r & Light Company SPENT FUEL HIGH DENSITY STORAGE RACKS Atese cell locations can not have St. Lucle Plant Unit No. 1 Unit 2 Fuel or consolidation canisters placed in them.

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July 11, 1989

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DISTRIBUTION"vile encl.

%Docket File

.~B PDII-2 Rdg.

DMiller JNorris DOCKET NO(S).

5 335/389 ftr. C. 0. Hoody, cting Senior Yice President-Nuclear Nuclear Energy Department Florida Power and Light Company P.O.

Box 14000 Juno Beach, PL 33408-0420

SUBJECT:

ST. LUCIE PLANT, UNIT NO. )

I dated dated Facility Operating License No.

, Amendment No.

Order Extending Construction Completion Date, dated Monthly Operating Report for transmitted by letter dated Annual/Semi-Annual Report-transmitted by letter dated The following documents concerning our review of the subject facility are transmitted for'our information.

P Notice of Recei pt of Appl icati on, dated Draft/Final Environmental Statement, dated Notice of Availability of Draft/Final Environmental Statement, dated Safety Evaluation Report, or Supplement No.

dated Environmental Assessment and Finding of No Significant Impact, dated Q Notice of Consideration of Issuance of Facility Operating License or Amendment to Facility Operating License, dated x Hi-Meekly Notice; Applications and Amendments to Operating Licenses Involving No Significant Hazards Considerations, dated 06/28/89

[8ee page(s)]

Exemption, dated Construction Permit No.

CPPR-

, Amendment No.

Enclosures:

As stated Division of Reac'Xor Projects, I/II Office of Nuclear Reactor Regulation cc:

See next page OFFICE)

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